But CoYo has denied the recall was linked to the woman’s death and accused Pret of hampering its own inquiry by failing to provide vital information.

“The claims made by Pret are unfounded,” a spokeswoman for CoYo said yesterday.

The latest death emerged as Pret was facing scrutiny over 15-year-old Natasha Ednan-Laperouse, who was allergic to sesame and died after eating one of its baguettes.

The second customer collapsed and died on 27 December last year after buying the sandwich in a store in Stall Street, Bath.

Pret said it had been “mis-sold” a guaranteed dairy-free yoghurt by CoYo that was discovered to contain dairy protein.

Vegan brand CoYo, a coconut milk brand that has been endorsed by TV cook Nigella Lawson, recalled the yoghurts in February. But yesterday, CoYo denied this was related, saying that product was supplied to it in January – after the woman’s death.

“The dairy-free product we provided to Pret in December 2017, at the time of this tragedy, is not linked to the product we recalled in February 2018,” a spokeswoman said.

“Pret’s inability to provide us with a batch code, despite several requests, has severely limited our ability to investigate this further.”